Organophotoreceptor with charge transport compound with hydrazone groups

ABSTRACT

This invention relates to a novel organophotoreceptor that includes a photoconductive layer having  
     a) a novel charge transport compound having the formula  
                 
 
     where R 1  is a carbazole group, a julolidine group, or a p-(N,N-disubstituted)arylamine, R 2 , R 3 , R 4 , R 5  and R 6  are, independently, an alkyl group or an aryl group, R 7  and R 8  are, independently, hydrogen, an alkyl group, or an aryl group, X is oxygen, sulfur, or a NR′ group where R′ is hydrogen, an alkyl, or an aryl group, and Y is a trivalent aryl group;  
     (b) a charge generating compound; and  
     wherein the at least one photoconductive layer is carried on an electrically conductive substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to copending U.S. ProvisionalPatent Applications serial No. 60/421,182 to Getautis et al., entitled“Electrophotographic Photoreceptor With Novel Charge TransportCompound,” incorporated herein by reference.

FIELD OF THE INVENTION

[0002] This invention relates to organophotoreceptors suitable for usein electrophotography and, more specifically, to organophotoreceptorshaving an improved charge transport compound having at least twohydrazone groups.

BACKGROUND OF THE INVENTION

[0003] In electrophotography, an organophotoreceptor in the form of aplate, disk, sheet, belt, drum or the like having an electricallyinsulating photoconductive element on an electrically conductivesubstrate is imaged by first uniformly electrostatically charging thesurface of the photoconductive layer, and then exposing the chargedsurface to a pattern of light. The light exposure selectively dissipatesthe charge in the illuminated areas where light strikes the surface,thereby forming a pattern of charged and uncharged areas, referred to asa latent image. A liquid or solid toner is then provided in the vicinityof the latent image, and toner droplets or particles deposit in thevicinity of either the charged or uncharged areas to create a tonedimage on the surface of the photoconductive layer. The resulting tonedimage can be transferred to a suitable ultimate or intermediatereceiving surface, such as paper, or the photoconductive layer canoperate as an ultimate receptor for the image. The imaging process canbe repeated many times to complete a single image, for example, byoverlaying images of distinct color components or effect shadow images,such as overlaying images of distinct colors to form a full color finalimage, and/or to reproduce additional images.

[0004] Both single layer and multilayer photoconductive elements havebeen used. In single layer embodiments, a charge transport material andcharge generating material are combined with a polymeric binder and thendeposited on the electrically conductive substrate. In multilayerembodiments, the charge transport material and charge generatingmaterial are present in the element in separate layers, each of whichcan optionally be combined with a polymeric binder, deposited on theelectrically conductive substrate. Two arrangements are possible. In onetwo-layer arrangement (the “dual layer” arrangement), the chargegenerating layer is deposited on the electrically conductive substrateand the charge transport layer is deposited on top of the chargegenerating layer. In an alternate two-layer arrangement (the “inverteddual layer” arrangement), the order of the charge transport layer andcharge generating layer is reversed.

[0005] In both the single and multilayer photoconductive elements, thepurpose of the charge generating material is to generate charge carriers(i.e., holes and/or electrons) upon exposure to light. The purpose ofthe charge transport material is to accept at least one type of thesecharge carriers, generally holes, and transport them through the chargetransport layer in order to facilitate discharge of a surface charge onthe photoconductive element. The charge transport material can be acharge transport compound, an electron transport compound, or acombination of both. When a charge transport compound is used, thecharge transport compound accepts the hole carriers and transports themthrough the layer with the charge transport compound. When an electrontransport compound is used, the electron transport compound accepts theelectron carriers and transports them through the layer with theelectron transport compound.

SUMMARY OF THE INVENTION

[0006] This invention provides novel organophotoreceptors having goodelectrostatic properties such as high V_(acc) and low V_(dis).

[0007] In a first aspect, an organophotoreceptor comprises at least aphotoconductive element comprising:

[0008] a) a charge transport compound having the formula

[0009] where R₁ is a carbazole group, a julolidine group, or ap-(N,N-disubstituted)arylamine, R₂, R₃, R₄, R₅ and R₆ are,independently, an alkyl group or an aryl group, R₇ and R₈ are,independently, hydrogen, an alkyl group, or an aryl group, X is oxygen,sulfur, or a NR′ group where R′ is hydrogen, an alkyl, or an aryl group,and Y is a aryl group; and

[0010] (b) a charge generating compound;

[0011] wherein the photoconductive element is on an electricallyconductive substrate.

[0012] The organophotoreceptor may be provided in the form of a plate, aflexible belt, a flexible disk, a sheet, a rigid drum, or a sheet arounda rigid or compliant drum. In one embodiment, the organophotoreceptorincludes: (a) a photoconductive element comprising the charge transportcompound, the charge generating compound, the electron transportcompound, and a polymeric binder; and (b) the electrically conductivesubstrate.

[0013] In a second aspect, the invention features an electrophotographicimaging apparatus that comprises (a) a light imaging component; and (b)the above-described organophotoreceptor oriented to receive light fromthe light imaging component. The apparatus can further comprise a liquidtoner dispenser. The method of electrophotographic imaging withphotoreceptors containing the above noted charge transport compounds isalso described.

[0014] In a third aspect, the invention features an electrophotographicimaging process that includes (a) applying an electrical charge to asurface of the above-described organophotoreceptor; (b) imagewiseexposing the surface of the organophotoreceptor to radiation todissipate charge in selected areas and thereby form a pattern of atleast relatively charged and uncharged areas on the surface; (c)contacting the surface with a toner, such as a liquid toner thatincludes a dispersion of colorant particles in an organic liquid, tocreate a toned image; and (d) transferring the toned image to asubstrate.

[0015] In a fourth aspect, the invention features a charge transportcompound having the general formula (1) above.

[0016] The invention provides suitable charge transport compounds fororganophotoreceptors featuring a combination of good mechanical andelectrostatic properties. These photoreceptors can be used successfullywith liquid toners to produce high quality images. The high quality ofthe imaging system can be maintained after repeated cycling.

[0017] Other features and advantages of the invention will be apparentfrom the following description of the particular embodiments thereof,and from the claims.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0018] An organophotoreceptor as described herein has an electricallyconductive substrate and a photoconductive element comprising a chargegenerating compound and a charge transport compound having two hydrazonegroups linked through an aryl group. These charge transport compoundshave desirable properties as evidenced by their performance inorganophotoreceptors for electrophotography. In particular, the chargetransport compounds of this invention have high charge carriermobilities and good compatibility with various binder materials, can becross-linked in both the single and multilayer photoconductive elements,and possess excellent electrophotographic properties. Theorganophotoreceptors according to this invention generally have a highphotosensitivity, a low residual potential, and a high stability withrespect to cycle testing, crystallization, and organophotoreceptorbending and stretching. The organophotoreceptors are particularly usefulin laser printers and the like as well as photocopiers, scanners andother electronic devices based on electrophotography. The use of thesecharge transport compounds is described in more detail below in thecontext of laser printer use, although their application in otherdevices operating by electrophotography can be generalized from thediscussion below.

[0019] To produce high quality images, particularly after multiplecycles, it is desirable for the charge transport compounds to form ahomogeneous solution with the polymeric binder and remain approximatelyhomogeneously distributed through the organophotoreceptor materialduring the cycling of the material. In addition, it is desirable toincrease the amount of charge that the charge transport material, suchas a charge transport compound, can accept (indicated by a parameterknown as the acceptance voltage or “V_(acc)”), and to reduce retentionof that charge upon discharge (indicated by a parameter known as thedischarge voltage or “V_(dis)”).

[0020] There are many charge transport compounds available forelectrophotography. Examples of charge transport compounds include, forexample, pyrazoline derivatives, fluorene derivatives, oxadiazolederivatives, stilbene derivatives, hydrazone derivatives, carbazolehydrazone derivatives, triaryl amines, polyvinyl carbazole, polyvinylpyrene, polyacenaphthylene, or multi-hydrazone compounds comprising atleast two hydrazone groups and at least two groups selected from thegroup consisting of p-(N,N-discubstituted) arylamine such astriphenylamine and heterocycles such as carbazole, julolidine,phenothiazine, phenazine, phenoxazine, phenoxathin, thiazole, oxazole,isoxazole, dibenzo(1,4)dioxine, thianthrene, imidazole, benzothiazole,benzotriazole, benzoxazole, benzimidazole, quinoline, isoquinoline,quinoxaline, indole, indazole, pyrrole, purine, pyridine, pyridazine,pyrimidine, pyrazine, triazole, oxadiazole, tetrazole, thiadiazole,benzisoxazole, benzisothiazole, dibenzofuran, dibenzothiophene,thiophene, thianaphthene, quinazoline, or cinnoline. However, there is aneed for other charge transport compounds to meet the variousrequirements of particular electrophotography applications.

[0021] In electrophotography applications, a charge generating compoundwithin an organophotoreceptor absorbs light to form electron-hole pairs.These electron-hole pairs can be transported over an appropriate timeframe under a large electric field to discharge locally a surface chargethat is generating the field. The discharge of the field at a particularlocation results in a surface charge pattern that essentially matchesthe pattern drawn with the light. This charge pattern then can be usedto guide toner deposition. The charge transport compounds describedherein are especially effective at transporting charge, and inparticular holes from the electron-hole pairs formed by the chargegenerating compound. In some embodiments, a specific electron transportcompound can also be used along with the charge transport compound.

[0022] The layer or layers of materials containing the charge generatingcompound and the charge transport compounds are within anorganophotoreceptor. To print a two dimensional image using theorganophotoreceptor, the organophotoreceptor has a two dimensionalsurface for forming at least a portion of the image. The imaging processthen continues by cycling the organophotoreceptor to complete theformation of the entire image and/or for the processing of subsequentimages.

[0023] The organophotoreceptor may be provided in the form of a plate, aflexible belt, a disk, a rigid drum, a sheet around a rigid or compliantdrum, or the like. The charge transport compound can be in the samelayer as the charge generating compound and/or in a different layer fromthe charge generating compound. Additional layers can be used also, asdescribed further below.

[0024] In some embodiments, the organophotoreceptor material comprises,for example: (a) a charge transport layer comprising the chargetransport compound and a polymeric binder; (b) a charge generating layercomprising the charge generating compound and a polymeric binder; and(c) the electrically conductive substrate. The charge transport layermay be intermediate between the charge generating layer and theelectrically conductive substrate. Alternatively, the charge generatinglayer may be intermediate between the charge transport layer and theelectrically conductive substrate. In further embodiments, theorganophotoreceptor material has a single layer with both a chargetransport compound and a charge generating compound within a polymericbinder.

[0025] The organophotoreceptors can be incorporated into anelectrophotographic imaging apparatus, such as laser printers. In thesedevices, an image is formed from physical embodiments and converted to alight image that is scanned onto the organophotoreceptor to form asurface latent image. The surface latent image can be used to attracttoner onto the surface of the organophotoreceptor, in which the tonerimage is the same or the negative of the light image projected onto theorganophotoreceptor. The toner can be a liquid toner or a dry toner. Thetoner is subsequently transferred, from the surface of theorganophotoreceptor, to a receiving surface, such as a sheet of paper.After the transfer of the toner, the entire surface is discharged, andthe material is ready to cycle again. The imaging apparatus can furthercomprise, for example, a plurality of support rollers for transporting apaper receiving medium and/or for movement of the photoreceptor, a lightimaging component with suitable optics to form the light image, a lightsource, such as a laser, a toner source and delivery system and anappropriate control system.

[0026] An electrophotographic imaging process generally can comprise (a)applying an electrical charge to a surface of the above-describedorganophotoreceptor; (b) imagewise exposing the surface of theorganophotoreceptor to radiation to dissipate charge in selected areasand thereby form a pattern of charged and uncharged areas on thesurface; (c) exposing the surface with a toner, such as a liquid tonerthat includes a dispersion of colorant particles in an organic liquid tocreate a toner image, to attract toner to the charged or dischargedregions of the organophotoreceptor; and (d) transferring the toner imageto a substrate.

[0027] As described herein, an organophotoreceptor comprises a chargetransport compound having the formula

[0028] where R₁ is a carbazole group, a julolidine group, or ap-(N,N-disubstituted)arylamine, R₂, R₃, R₄, R₅ and R₆ are,independently, an alkyl group or an aryl group, R₇ and R₈ are,independently, hydrogen, an alkyl group or an aryl group, X is oxygen,sulfur, or a NR′ group where R′ is hydrogen, an alkyl, or an aryl group,and Y is an aryl group.

[0029] Substitution is liberally allowed on the chemical groups toeffect various physical effects on the properties of the compounds, suchas mobility, sensitivity, solubility, stability, and the like, as isknown generally in the art. In the description of chemical substituents,there are certain practices common to the art that are reflected in theuse of language. The term group indicates that the generically recitedchemical entity (e.g., alkyl group, phenyl group, julolidine group,(N,N-disubstituted) arylamine group, etc.) may have any substituentthereon which is consistent with the bond structure of that group. Forexample, where the term ‘alkyl group’ is used, that term would not onlyinclude unsubstituted liner, branched and cyclic alkyls, such as methyl,ethyl, isopropyl, tert-butyl, cyclohexyl, dodecyl and the like, but alsosubstitutents such as hydroxyethyl, cyanobutyl, 1,2,3-trichloropropane,and the like. However, as is consistent with such nomenclature, nosubstitution would be included within the term that would alter thefundamental bond structure of the underlying group. For example, where aphenyl group is recited, substitution such as 1-hydroxyphenyl,2,4-fluorophenyl, orthocyanophenyl, 1,3,5-trimethoxyphenyl and the likewould be acceptable within the terminology, while substitution of1,1,2,2,3,3-hexamethylphenyl would not be acceptable as thatsubstitution would require the ring bond structure of the phenyl groupto be altered to a non-aromatic form because of the substitution.Similarly, when referring to carbazole group or julolidine group, thecompound or substitutent cited will include any substitution that doesnot substantively alter the chemical nature of the carbazole ring or thejulolidine ring in the formula. When referringp-(N,N-disubstituted)arylamine group, the two substituents attached tothe nitrogen may be any group that will not substantively alter thechemical nature of the amine group. Where the term moiety is used, suchas alkyl moiety or phenyl moiety, that terminology indicates that thechemical material is not substituted. Where the term alkyl moiety isused, that term represents only an unsubstituted alkyl hydrocarbongroup, whether branched, straight chain, or cyclic.

[0030] Organophotoreceptors

[0031] The organophotoreceptor may be, for example, in the form of aplate, a sheet, a flexible belt, a disk, a rigid drum, or a sheet arounda rigid or compliant drum, with flexible belts and rigid drums generallybeing used in commercial embodiments. The organophotoreceptor maycomprise, for example, an electrically conductive substrate and on theelectrically conductive substrate a photoconductive element in the formof one or more layers. The photoconductive element can comprise both acharge transport compound and a charge generating compound in apolymeric binder, which may or may not be in the same layer, as well asan electron transport compound in some embodiments. For example, thecharge transport compound and the charge generating compound can be in asingle layer. In other embodiments, however, the photoconductive elementcomprises a bilayer construction featuring a charge generating layer anda separate charge transport layer. The charge generating layer may belocated intermediate between the electrically conductive substrate andthe charge transport layer. Alternatively, the photoconductive elementmay have a structure in which the charge transport layer is intermediatebetween the electrically conductive substrate and the charge generatinglayer.

[0032] The electrically conductive substrate may be flexible, forexample in the form of a flexible web or a belt, or inflexible, forexample in the form of a drum. A drum can have a hollow cylindricalstructure that provides for attachment of the drum to a drive thatrotates the drum during the imaging process. Typically, a flexibleelectrically conductive substrate comprises an electrically insulatingsubstrate and a thin layer of electrically conductive material ontowhich the photoconductive material is applied.

[0033] The electrically insulating substrate may be paper or a filmforming polymer such as polyester (e.g., polyethylene terepthalate orpolyethylene naphthalate), polyimide, polysulfone, polypropylene, nylon,polyester, polycarbonate, polyvinyl resin, polyvinyl fluoride,polystyrene and the like. Specific examples of polymers for supportingsubstrates included, for example, polyethersulfone (Stabar™ S-100,available from ICI), polyvinyl fluoride (Tedlar®, available from E.I.DuPont de Nemours & Company), polybisphenol-A polycarbonate (Makrofol™,available from Mobay Chemical Company) and amorphous polyethyleneterephthalate (Melinar™, available from ICI Americas, Inc.). Theelectrically conductive materials may be graphite, dispersed carbonblack, iodide, conductive polymers such as polypyroles and Calgon®conductive polymer 261 (commercially available from Calgon Corporation,Inc., Pittsburgh, Pa.), metals such as aluminum, titanium, chromium,brass, gold, copper, palladium, nickel, or stainless steel, or metaloxide such as tin oxide or indium oxide. In embodiments of particularinterest, the electrically conductive material is aluminum. Generally,the photoconductor substrate has a thickness adequate to provide therequired mechanical stability. For example, flexible web substratesgenerally have a thickness from about 0.01 to about 1 mm, while drumsubstrates generally have a thickness of from about 0.5 mm to about 2mm.

[0034] The charge generating compound is a material which is capable ofabsorbing light to generate charge carriers, such as a dye or pigment.Non-limiting examples of suitable charge generating compounds include,for example, metal-free phthalocyanines (e.g., ELA 8034 metal-freephthalocyanine available from H.W. Sands, Inc. or Sanyo Color Works,Ltd., CGM-X01), metal phthalocyanines such as titanium phthalocyanine,copper phthalocyanine, oxytitanium phthalocyanine (also referred to astitanyl oxyphthalocyanine, and including any crystalline phase ormixtures of crystalline phases that can act as a charge generatingcompound), hydroxygallium phthalocyanine, squarylium dyes and pigments,hydroxy-substituted squarylium pigments, perylimides, polynuclearquinones available from Allied Chemical Corporation under the tradenameIndofast® Double Scarlet, Indofast® Violet Lake B, Indofast® BrilliantScarlet and Indofast® Orange, quinacridones available from DuPont underthe tradename Monastral™ Red, Monastral™ Violet and Monastral™ Red Y,naphthalene 1,4,5,8-tetracarboxylic acid derived pigments including theperinones, tetrabenzoporphyrins and tetranaphthaloporphyrins, indigo-and thioindigo dyes, benzothioxanthene-derivatives, perylene3,4,9,10-tetracarboxylic acid derived pigments, polyazo-pigmentsincluding bisazo-, trisazo- and tetrakisazo-pigments, polymethine dyes,dyes containing quinazoline groups, tertiary amines, amorphous selenium,selenium alloys such as selenium-tellurium, selenium-tellurium-arsenicand selenium-arsenic, cadmium sulphoselenide, cadmium selenide, cadmiumsulphide, and mixtures thereof. For some embodiments, the chargegenerating compound comprises oxytitanium phthalocyanine (e.g., anyphase thereof), hydroxygallium phthalocyanine or a combination thereof.

[0035] The photoconductive layer of this invention may contain anelectron transport compound. Generally, any electron transport compoundknown in the art can be used. Non-limiting examples of suitable electrontransport compound include, for example, bromoaniline,tetracyanoethylene, tetracyanoquinodimethane,2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone,2,4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone,2,6,8-trinitro-indeno4H-indeno[1,2-b]thiophene-4-one, and1,3,7-trinitrodibenzo thiophene-5,5-dioxide,(2,3-diphenyl-1-indenylidene)malononitrile, 4H-thiopyran-1,1-dioxide andits derivatives such as4-dicyanomethylene-2,6-diphenyl-4H-thiopyran-1,1-dioxide,4-dicyanomethylene-2,6-di-m-tolyl-4H-thiopyran-1,1-dioxide, andunsym-metrically substituted 2,6-diaryl-4H-thiopyran-1,1-dioxide such as4H-1,1-dioxo-2-(p-isopropylphenyl)-6-phenyl-4-(dicyanomethylidene)thiopyranand4H-1,1-dioxo-2-(p-isopropylphenyl)-6-(2-thienyl)-4-(dicyanomethyl-idene)thiopyran,derivatives of phospha-2,5-cyclohexadiene,alkoxycarbonyl-9-fluorenylidene)malononitrile derivatives such as(4-n-butoxycarbonyl-9-fluorenylidene)malononitrile,(4-phenethoxycarbonyl-9-fluorenyl idene)malononitrile,(4-carbitoxy-9-fluorenylidene)malononitrile, and diethyl(4-n-butoxycarbonyl-2,7-dinitro-9-fluorenylidene)-malonate, anthraquinodimethanederivatives such as 11,11,12,12-tetracyano-2-alkylanthraquinodimethaneand 11,11-dicyano-12,12-bis(ethoxycarbonyl)anthraquinodimethane,anthrone derivatives such as1-chloro-10-[bis(ethoxycarbonyl)methylene]anthrone,1,8-dichloro-10-[bis(ethoxycarbonyl) methylene]anthrone,1,8-dihydroxy-10-[bis(ethoxycarbonyl)methylene]anthrone, and1-cyano-10-[bis(ethoxycarbonyl)methylene)anthrone,7-nitro-2-aza-9-fluroenylidene-malononitrile, diphenoquinonederivatives, benzoquinone derivatives, naphtoquinone derivatives,quinine derivatives, tetracyanoethylenecyanoethylene, 2,4,8-trinitrothioxantone, dinitrobenzene derivatives, dinitroanthracene derivatives,dinitroacridine derivatives, nitroanthraquinone derivatives,dinitroanthraquinone derivatives, succinic anhydride, maleic anhydride,dibromo maleic anhydride, pyrene derivatives, carbazole derivatives,hydrazone derivatives, N,N-dialkylaniline derivatives, diphenylaminederivatives, triphenylamine derivatives, triphenylmethane derivatives,tetracyano quinoedimethane, 2,4,5,7-tetranitro-9-fluorenone,2,4,7-trinitro-9-dicyanomethylene fluorenone, 2,4,5,7-tetranitroxanthonederivatives, and 2,4,8-trinitrothioxanthone derivatives. In someembodiments of interest, the electron transport compound comprises an(alkoxycarbonyl-9-fluorenylidene)malononitrile derivative, such as(4-n-butoxycarbonyl-9-fluorenylidene)malononitrile.

[0036] An electron transport compound and a UV light stabilizer can havea synergistic relationship for providing desired electron flow withinthe photoconductor. The presence of the UV light stabilizers alters theelectron transport properties of the electron transport compounds toimprove the electron transporting properties of the composite. UV lightstabilizers can be ultraviolet light absorbers or ultraviolet lightinhibitors that trap free radicals.

[0037] UV light absorbers can absorb ultraviolet radiation and dissipateit as heat. UV light inhibitors are thought to trap free radicalsgenerated by the ultraviolet light and after trapping of the freeradicals, subsequently to regenerate active stabilizer moieties withenergy dissipation. In view of the synergistic relationship of the UVstabilizers with electron transport compounds, the particular advantagesof the UV stabilizers may not be their UV stabilizing abilities,although the UV stabilizing ability may be further advantageous inreducing degradation of the organophotoreceptor over time. While notwanting to be limited by theory, the synergistic relationshipcontributed by the UV stabilizers may be related to the electronicproperties of the compounds, which contribute to the UV stabilizingfunction, by further contributing to the establishment of electronconduction pathways in combination with the electron transportcompounds. In particular, the organophotoreceptors with a combination ofthe electron transport compound and the UV stabilizer can demonstrate amore stable acceptance voltage V_(acc) with cycling. The improvedsynergistic performance of organophotoreceptors with layers comprisingboth an electron transport compound and a UV stabilizer are describedfurther in copending U.S. patent application Ser. No. 10/425,333 filedon Apr. 28, 2003 to Zhu, entitled “Organophotoreceptor With A LightStabilizer,” incorporated herein by reference.

[0038] Non-limiting examples of suitable light stablizer include, forexample, hindered trialkylamines such as Tinuvin 144 and Tinuvin 292(from Ciba Specialty Chemicals, Terrytown, N.Y.), hinderedalkoxydialkylamines such as Tinuvin 123 (from Ciba Specialty Chemicals),benzotriazoles such as Tinuvan 328, Tinuvin 900 and Tinuvin 928 (fromCiba Specialty Chemicals), benzophenones such as Sanduvor 3041 (fromClariant Corp., Charlotte, N.C.), nickel compounds such as Arbestab(from Robinson Brothers Ltd, West Midlands, Great Britain), salicylates,cyanocinnamates, benzylidene malonates, benzoates, oxanilides such asSanduvor VSU (from Clariant Corp., Charlotte, N.C.), triazines such asCyagard UV-1164 (from Cytec Industries Inc., N.J.), polymeric stericallyhindered amines such as Luchem (from Atochem North America, Buffalo,N.Y.). In some embodiments, the light stabilizer is selected from thegroup consisting of hindered trialkylamines having the followingformula:

[0039] where R₁, R₂, R₃, R₄, R₆, R₇, R₈, R₁₀, R₁₁, R₁₂, R₁₃, R₁₄, R₁₅are, independently, hydrogen, alkyl group, or ester, or ether group; andR₅, R₉, and R₁₄ are, independently, alkyl group; and X is a linkinggroup selected from the group consisting of —O—CO—(CH₂)_(m)—CO—O—where mis between 2 to 20.

[0040] The binder generally is capable of dispersing or dissolving thecharge transport compound (in the case of the charge transport layer ora single layer construction), the charge generating compound (in thecase of the charge generating layer or a single layer construction)and/or an electron transport compound for appropriate embodiments.Examples of suitable binders for both the charge generating layer andcharge transport layer generally include, for example,polystyrene-co-butadiene, polystyrene-co-acrylonitrile, modified acrylicpolymers, polyvinyl acetate, styrene-alkyd resins, soya-alkyl resins,polyvinylchloride, polyvinylidene chloride, polyacrylonitrile,polycarbonates, polyacrylic acid, polyacrylates, polymethacrylates,styrene polymers, polyvinyl butyral, alkyd resins, polyamides,polyurethanes, polyesters, polysulfones, polyethers, polyketones,phenoxy resins, epoxy resins, silicone resins, polysiloxanes,poly(hydroxyether) resins, polyhydroxystyrene resins, novolak,poly(phenylglycidyl ether)-co-dicyclopentadiene, copolymers of monomersused in the above-mentioned polymers, and combinations thereof. Suitablebinders include, for example, polyvinyl butyral, such as BX-1 and BX-5form Sekisui Chemical Co. Ltd., Japan.

[0041] Suitable optional additives for any one or more of the layersinclude, for example, antioxidants, coupling agents, dispersing agents,curing agents, surfactants and combinations thereof.

[0042] The photoconductive element overall typically has a thicknessfrom about 10 to about 45 microns. In the dual layer embodiments havinga separate charge generating layer and a separate charge transportlayer, charge generation layer generally has a thickness form about 0.5to about 2 microns, and the charge transport layer has a thickness fromabout 5 to about 35 microns. In embodiments in which the chargetransport compound and the charge generating compound are in the samelayer, the layer with the charge generating compound and the chargetransport composition generally has a thickness from about 7 to about 30microns. In embodiments with a distinct electron transport layer, theelectron transport layer has an average thickness from about 0.5 micronsto about 10 microns and in further embodiments from about 1 micron toabout 3 microns. In general, an electron transport overcoat layer canincrease mechanical abrasion resistance, increases resistance to carrierliquid and atmospheric moisture, and decreases degradation of thephotoreceptor by corona gases. A person of ordinary skill in the artwill recognize that additional ranges of thickness within the explicitranges above are contemplated and are within the present disclosure.

[0043] Generally, for the organophotoreceptors described herein, thecharge generation compound is in an amount from about 0.5 to about 25weight percent in further embodiments in an amount from about 1 to about15 weight percent and in other embodiments in an amount from about 2 toabout 10 weight percent, based on the weight of the photoconductivelayer. The charge transport compound is in an amount from about 10 toabout 80 weight percent, based on the weight of the photoconductivelayer, in further embodiments in an amount from about 35 to about 60weight percent, and in other embodiments from about 45 to about 55weight percent, based on the weight of the photoconductive layer. Theoptional electron transport compound, when present, can be in an amountof at least about 2 weight percent, in other embodiments from about 2.5to about 25 weight percent, based on the weight of the photoconductivelayer, and in further embodiments in an amount from about 4 to about 20weight percent, based on the weight of the photoconductive layer. Thebinder is in an amount from about 15 to about 80 weight percent, basedon the weight of the photoconductive layer, and in further embodimentsin an amount from about 20 to about 75 weight percent, based on theweight of the photoconductive layer. A person of ordinary skill in theart will recognize that additional ranges within the explicit ranges ofcompositions are contemplated and are within the present disclosure.

[0044] For the dual layer embodiments with a separate charge generatinglayer and a charge transport layer, the charge generation layergenerally comprises a binder in an amount from about 10 to about 90weight percent, in further embodiments from about 15 to about 80 weightpercent and in some embodiments in an amount of from about 20 to about75 weight percent, based on the weight of the charge generation layer.The optional electron transport compound in the charge generating layer,if present, generally can be in an amount of at least about 2.5 weightpercent, in further embodiments from about 4 to about 30 weight percentand in other embodiments in an amount from about 10 to about 25 weightpercent, based on the weight of the charge generating layer. The chargetransport layer generally comprises a binder in an amount from about 20weight percent to about 70 weight percent and in further embodiments inan amount from about 30 weight percent to about 50 weight percent. Aperson of ordinary skill in the art will recognize that additionalranges of binder concentrations for the dual layer embodiments withinthe explicit ranges above are contemplated and are within the presentdisclosure.

[0045] For the embodiments with a single layer having a chargegenerating compound and a charge transport compound, the photoconductivelayer generally comprises a binder, a charge transport compound and acharge generation compound. The charge generation compound can be in anamount from about 0.05 to about 25 weight percent and in furtherembodiment in an amount from about 2 to about 15 weight percent, basedon the weight of the photoconductive layer. The charge transportcompound can be in an amount from about 10 to about 80 weight percent,in other embodiments from about 25 to about 65 weight percent, inadditional embodiments from about 30 to about 60 weight percent and infurther embodiments in an amount of from about 35 to about 55 weightpercent, based on the weight of the photoconductive layer, with theremainder of the photoconductive layer comprising the binder, andoptionally additives, such as any conventional additives. A single layerwith a charge transport composition and a charge generating compoundgenerally comprises a binder in an amount from about 10 weight percentto about 75 weight percent, in other embodiments from about 20 weightpercent to about 60 weight percent, and in further embodiments fromabout 25 weight percent to about 50 weight percent. Optionally, thelayer with the charge generating compound and the charge transportcompound may comprise an electron transport compound. The optionalelectron transport compound, if present, generally can be in an amountof at least about 2.5 weight percent, in further embodiments from about4 to about 30 weight percent and in other embodiments in an amount fromabout 10 to about 25 weight percent, based on the weight of thephotoconductive layer. A person of ordinary skill in the art willrecognize that additional composition ranges within the explicitcompositions ranges for the layers above are contemplated and are withinthe present disclosure.

[0046] In general, any layer with an electron transport layer canadvantageously further include a UV light stabilizer. In particular, theelectron transport layer generally can comprise an electron transportcompound, a binder and an optional UV light stabilizer. An overcoatlayer comprising an electron transport compound is described further incopending U.S. patent application Ser. No. 10/396,536 to Zhu et al.entitled, “Organophotoreceptor With An Electron Transport Layer,”incorporated herein by reference. For example, an electron transportcompound as described above may be used in the release layer of thephotoconductors described herein. The electron transport compound in anelectron transport layer can be in an amount from about 10 to about 50weight percent, and in other embodiments in an amount from about 20 toabout 40 weight percent, based on the weight of the electron transportlayer. A person of ordinary skill in the art will recognize thatadditional ranges of compositions within the explicit ranges arecontemplated and are within the present disclosure.

[0047] The UV light stabilizer, if present, in any of one or moreappropriate layers of the photoconductor generally is in an amount fromabout 0.5 to about 25 weight percent and in some embodiments in anamount from about 1 to about 10 weight percent, based on the weight ofthe particular layer. A person of ordinary skill in the art willrecognize that additional ranges of compositions within the explicitranges are contemplated and are within the present disclosure.

[0048] For example, the photoconductive layer may be formed bydispersing or dissolving the components, such as one or more of a chargegenerating compound, a charge transport compound, an electron transportcompound, a UV light stabilizer, and a polymeric binder in organicsolvent, coating the dispersion and/or solution on the respectiveunderlying layer and drying the coating. In particular, the componentscan be dispersed by high shear homogenization, ball-milling, attritormilling, high energy bead (sand) milling or other size reductionprocesses or mixing means known in the art for effecting particle sizereduction in forming a dispersion.

[0049] The photoreceptor may optionally have one or more additionallayers as well. An additional layer can be, for example, a sub-layer oran overcoat layer, such as a barrier layer, a release layer, aprotective layer, or an adhesive layer. A release layer or a protectivelayer may form the uppermost layer of the photoconductor element. Abarrier layer may be sandwiched between the release layer and thephotoconductive element or used to overcoat the photoconductive element.The barrier layer provides protection from abrasion to the underlayers.An adhesive layer locates and improves the adhesion between aphotoconductive element, a barrier layer and a release layer, or anycombination thereof. A sub-layer is a charge blocking layer and locatesbetween the electrically conductive substrate and the photoconductiveelement. The sub-layer may also improve the adhesion between theelectrically conductive substrate and the photoconductive element.

[0050] Suitable barrier layers include, for example, coatings such ascrosslinkable siloxanol-colloidal silica coating and hydroxylatedsilsesquioxane-colloidal silica coating, and organic binders such aspolyvinyl alcohol, methyl vinyl ether/maleic anhydride copolymer,casein, polyvinyl pyrrolidone, polyacrylic acid, gelatin, starch,polyurethanes, polyimides, polyesters, polyamides, polyvinyl acetate,polyvinyl chloride, polyvinylidene chloride, polycarbonates, polyvinylbutyral, polyvinyl acetoacetal, polyvinyl formal, polyacrylonitrile,polymethyl methacrylate, polyacrylates, polyvinyl carbazoles, copolymersof monomers used in the above-mentioned polymers, vinyl chloride/vinylacetate/vinyl alcohol terpolymers, vinyl chloride/vinyl acetate/maleicacid terpolymers, ethylene/vinyl acetate copolymers, vinylchloride/vinylidene chloride copolymers, cellulose polymers, andmixtures thereof. The above barrier layer polymers optionally maycontain small inorganic particles such as fumed silica, silica, titania,alumina, zirconia, or a combination thereof. Barrier layers aredescribed further in U.S. Pat. No. 6,001,522 to Woo et al., entitled“Barrier Layer For Photoconductor Elements Comprising An Organic PolymerAnd Silica,” incorporated herein by reference. The release layer topcoatmay comprise any release layer composition known in the art. In someembodiments, the release layer is a fluorinated polymer, siloxanepolymer, fluorosilicone polymer, silane, polyethylene, polypropylene,polyacrylate, or a combination thereof. The release layers can comprisecrosslinked polymers.

[0051] The release layer may comprise, for example, any release layercomposition known in the art. In some embodiments, the release layercomprises a fluorinated polymer, siloxane polymer, fluorosiliconepolymer, polysilane, polyethylene, polypropylene, polyacrylate,poly(methyl methacrylate-co-methacrylic acid), urethane resins,urethane-epoxy resins, acrylated-urethane resins, urethane-acrylicresins, or a combination thereof. In further embodiments, the releaselayers comprise crosslinked polymers.

[0052] The protective layer can protect the organophotoreceptor fromchemical and mechanical degradation. The protective layer may compriseany protective layer composition known in the art. In some embodiments,the protective layer is a fluorinated polymer, siloxane polymer,fluorosilicone polymer, polysilane, polyethylene, polypropylene,polyacrylate, poly(methyl methacrylate-co-methacrylic acid), urethaneresins, urethane-epoxy resins, acrylated-urethane resins,urethane-acrylic resins, or a combination thereof. In some embodimentsof particular interest, the release layers are crosslinked polymers.

[0053] An overcoat layer may comprise an electron transport compound asdescribed further in copending U.S. patent application Ser. No.10/396,536, filed on Mar. 25, 2003 to Zhu et al. entitled,“Organoreceptor With An Electron Transport Layer,” incorporated hereinby reference. For example, an electron transport compound, as describedabove, may be used in the release layer of this invention. The electrontransport compound in the overcoat layer can be in an amount from about2 to about 50 weight percent, and in other embodiments in an amount fromabout 10 to about 40 weight percent, based on the weight of the releaselayer. A person of ordinary skill in the art will recognize thatadditional ranges of composition within the explicit ranges arecontemplated and are within the present disclosure.

[0054] Generally, adhesive layers comprise a film forming polymer, suchas polyester, polyvinylbutyral, polyvinylpyrolidone, polyurethane,polymethyl methacrylate, poly(hydroxy amino ether) and the like.

[0055] Sub-layers can comprise, for example, polyvinylbutyral,organosilanes, hydrolyzable silanes, epoxy resins, polyesters,polyamides, polyurethanes, silicones and the like. In some embodiments,the sub-layer has a dry thickness between about 20 Angstroms and about2,000 Angstroms. Sublayers containing metal oxide conductive particlescan be between about 1 and about 25 microns thick. A person of ordinaryskill in the art will recognize that additional ranges of compositionsand thickness within the explicit ranges are contemplated and are withinthe present disclosure.

[0056] The charge transport compounds as described herein, andphotoreceptors including these compounds, are suitable for use in animaging process with either dry or liquid toner development. Forexample, any dry toners and liquid toners known in the art may be usedin the process and the apparatus of this invention. Liquid tonerdevelopment can be desirable because it offers the advantages ofproviding higher resolution images and requiring lower energy for imagefixing compared to dry toners. Examples of suitable liquid toners areknown in the art. Liquid toners generally comprise toner particlesdispersed in a carrier liquid. The toner particles can comprise acolorant/pigment, a resin binder, and/or a charge director. In someembodiments of liquid toner, a resin to pigment ratio can be from 1:1 to10:1, and in other embodiments, from 4:1 to 8:1. Liquid toners aredescribed further in Published U.S. Patent Applications 2002/0128349,entitled “Liquid Inks Comprising A Stable Organosol,” 2002/0086916,entitled “Liquid Inks Comprising Treated Colorant Particles,” and2002/0197552, entitled “Phase Change Developer For LiquidElectrophotography,” all three of which are incorporated herein byreference.

[0057] Charge Transport Compound

[0058] As described herein, an organophotoreceptor comprises a chargetransport compound having the formula

[0059] where R₁ is a carbazole group, a julolidine group, or ap-(N,N-disubstituted)arylamine, R₂, R₃, R₄, R₅ and R₆ are,independently, hydrogen, an alkyl group or an aryl group, R₇ and R₈ are,independently, hydrogen, an alkyl group, or an aryl group, X is oxygen,sulfur, or a NR′ group where R′ is hydrogen, an alkyl, or an aryl group,and Y is an aryl group. As noted in formula (1), Y is at leasttrivalent. Non-limiting examples of trivalent aryl groups that aresuitable as Y have the following formulae:

[0060] Specific, non-limiting examples of suitable charge transportcompounds within the general Formula (1) of the present invention havethe following structures.

[0061] Synthesis of Charge Transport Compounds

[0062] In general, the charge transport compounds can be prepared as twoprecursors, each having a hydrazone group that are then reacted to formthe charge transport compound. Specifically, one precursor can be formedwith the structure

[0063] where R₁, R₂ and R₈ are selected to yield the desired specificstructure within the general structure of formula (1) above. The secondprecursor has the structure

[0064] where R₃, R₄, R₅, R₆, and X are selected to yield the desiredspecific structure within the general framework of formula (1) above.The active hydrogen on the X group adds to the epoxy group to form theproduct under alkaline catalysis for an epoxy reaction.

[0065] Synthesis of First Precursor Of Formula (7) The charge transportcompounds with a hydrazone bonded to the epoxy group generally aresynthesized by forming the desired substituted hydrazone, which isreacted at the secondary amine to form the epoxy group. In particular,the aromatic-substituted secondary amine reacts with the epichlorhydrinby way of the active hydrogen of the secondary amine in a base catalyzedreaction to form the epoxy group with a —CH₂— group between the epoxygroup and the amine. The hydrazone is formed from the reaction of anaryl substituted hydrazine with an aldehyde or ketone having aN,N-disubstituted arylamine, as describe further below. Suitablehydrazines and arylamines are described further below.

[0066] The aromatic-substituted hydrazine supplies the R₂ group fromformula (7) above, and an N,N-disubstituted amino aryl substitutedaldehyde or ketone supplies the R₁ group of formula (7). In the reactionof the aldehyde or ketone with the hydrazine, the oxygen of thealdehyde/ketone group is replaced with the double bonded carbon.

[0067] Hydrazines

[0068] The synthesis of some representative hydrzines is described inthe following.

[0069] 1,1-Dinaphthylhydrazine

[0070] 1,1-Dinaphthylhydrazine can be prepared according to theprocedure described in Staschkow, L. I.; Matevosyan, R. O. Journal ofthe General Chemistry (1964) 34, 136, which is incorporated herein byreference. A suspension of 0.07 mole of the naphthyl nitrosamine in 750ml of ether is cooled to 5-8° C. and treated with 150 g of zinc dust.Acetic acid (70 ml) is then added drop wise with stirring. To completethe reaction, 40 g of zinc dust is added. The reaction mixture is heatedand filtered from the sludge. The mother liquor is washed with 10%sodium carbonate solution and dried with solid KOH. The ether isdistilled off to give the crystalline hydrazine, which is crystallizedfrom ethanol or butanol. Other symmetric disubstituted hydrazines can besynthesized based on an equivalent process.

[0071] N-Phenyl-N-sulfolan-3-ylhydrazine

[0072] N-Phenyl-N-sulfolan-3-ylhydrazine can be prepared according tothe procedure described in Great Britain Patent No. 1,047,525 by Mason,which is incorporated herein by reference. To a mixture of 0.5 mole ofbutadiene sulfone (commercially available from Aldrich, Milwaukee, Wis.)and 0.55 mole of phenylhydrazine (commercially available from Aldrich,Milwaukee, Wis.) was added 0.005 mole 40% aqueous potassium hydroxidesolution. The mixture was kept for 2 hours at 60° C. whereupon a solidseparated. After 10 hours the solid was filtered off to giveN-phenyl-N-sulfolan-3-ylhydrazine (53%) having a melting point of120-121° C. (MeOH).

[0073] N-Pyrrol-2-yl-N-phenylhydrazine

[0074] N-Pyrrol-2-yl-N-phenylhydrazine can be prepared according to theprocedure described in Japanese Patent No. 05148210 by Myamoto,incorporated herein by reference.

[0075] 1-Phenyl-1-(1-benzyl-1H-tetrazol-5-yl)hydrazine

[0076] 1-Phenyl-1-(1-benzyl-1H-tetrazol-5-yl)hydrazine can be preparedaccording to the procedure described in Tetrahedron (1983), 39(15),2599-608 by Atherton et al., incorporated herein by reference.

[0077] N-(4-Stilbenyl)-N-phenylhydrazine

[0078] N-(4-Stilbenyl)-N-phenylhydrazine can be prepared according tothe procedure described in Zh. Org. Khim. (1967), 3(9), 1605-3 byMatevosyan et al., incorporated herein by reference. Following thisprocedure, to a mixture of phenylhydrazine (97 g, 0.9 mole, commerciallyavailable from Aldrich, Milwaukee, Wis.) and p-chlorostilbene (21.4 g,0.1 mole, commercially available from Spectrum Quality Products, Inc.,Gardena, Calif.; Web: www.spectrumchemical.com) heated to boilingtemperature, sodium was slowly added until there was no more dischargeof red coloration. After boiling for some time the mixture was dissolvedin 1750 ml of ethanol and cooled to −15° C. The precipitated product wasrecrystallized to give 28% of N-(4-stilbenyl)-N-phenylhydrazine.

[0079] N-(5-Benzotriazolyl)-N-phenylhydrazine

[0080] N-(5-benzotriazolyl)-N-phenylhydrazine can be prepared accordingto the procedure that follows. To a mixture of phenylhydrazine (97 g,0.9 mole, commercially available from Aldrich, Milwaukee, Wis.) and5-chlorobenzotriazole (15.4 g, 0.1 mole, commercially available fromAldrich, Milwaukee, Wis.) heated to boiling temperature, sodium isslowly added until there is no more discharge of red coloration. Afterboiling for some time the mixture is cooled to room temperature. Theproduct is isolated and purified.

[0081] N-Phenyl-N-sulfolan-3-ylhydrazine

[0082] N-Phenyl-N-sulfolan-3-ylhydrazine can be prepared according tothe procedure described in Great Britain Patent No. 1,047,525 by Mason,incorporated herein by reference. Following this procedure, to a mixtureof 0.5 mole of butadiene sulfone (commercially available from Aldrich,Milwaukee, Wis.) and 0.55 mole of phenylhydrazine (commerciallyavailable from Aldrich, Milwaukee, Wis.), a 0.005 mole 40% aqueouspotassium hydroxide solution was added. The mixture was kept for 2 hoursat 60° C. whereupon a solid separated. After 10 hours the solid wasfiltered off to give N-phenyl-N-sulfolan-3-ylhydrazine (I) (93%) havinga melting point of 119-20° C. (MeOH).

[0083] N-4-[(9H-fluoren-9-ylidene)benzyl]-N-phenylhydrazine

[0084] N-4-[(9H-fluoren-9-ylidene)benzyl]-N-phenylhydrazine can beprepared according to the procedure similar to that described in Zh.Org. Khim. (1967), 3(9), 1605-3 by Matevosyan et al., incorporatedherein by reference. Following this procedure, to a mixture ofphenylhydrazine (97 g, 0.9 mole, commercially available from Aldrich,Milwaukee, Wis.) and p-9-(4-chlorobenzylidene)fluorene (28.9 g, 0.1mole, commercially available from from Aldrich, Milwaukee, Wis.) heatedto boiling temperature, sodium was slowly added until there was no moredischarge of red coloration. After boiling for some time the mixture wasdissolved in 1750 ml of ethanol and cooled to −15° C. The precipitatedproduct was recrystallized to giveN-4-[(9H-fluoren-9-ylidene)benzyl]-N-phenylhydrazine.

[0085] 5-Methyl-1-Phenyl-3-(1-Phenylhydrazino)-Pyrazole

[0086] 5-Methyl-1-phenyl-3-(1-phenylhydrazino)-pyrazole can be preparedaccording to the procedure described in J. Chem. Soc. C (1971), (12),2314-17 by Boyd et al., incorporated herein by reference.

[0087] 4-Methylsulfonylphenylhydrazine (Registry Number 877-66-7)

[0088] 4-Methylsulfonylphenylhydrazine is commercially available fromFisher Scientific USA, Pittsburgh, Pa. (1-800-766-7000).

[0089] 1,1′-(Sulfonyldi-4,1-phenylene)bishydrazine (Registry Number14052-65-4)

[0090] 1,1′-(Sulfonyldi-4,1-phenylene)bishydrazine dihydrochloride iscommercially available from Vitas-M, Moscow, Russia; (Phone: 7 095 9395737)

[0091] Aralaldehydes

[0092] Representative arylaldehydes for reacting with the hydrozones canbe obtained as follows.

[0093] Synthesis Of Julolidine Aldehyde

[0094] Julolidine (100 g, 0.6 moles, commercially obtained from AldrichChemicals Co, Milwaukee, Wis. 53201) was dissolved in DMF (200 ml,commercially obtained from Aldrich) in a 500 ml three neck round bottomflask. The flask was cooled to 0° C. in ice bath. POCl₃ (107 g, 0.7mole, Aldrich) was added drop wise while keeping the temperature below5° C. After the addition of POCl₃ was completed, the flask was warmed toroom temperature and placed in a steam bath while stirring for a periodof 1 hour. The flask was cooled to room temperature and the solution wasadded slowly to a large excess of distilled water with good agitation.Stirring was continued for additional 2 hours. The solid was filteredoff and washed repeatedly with water until the effluent water becameneutral. The product was dried in vacuum oven at 50 C. for 4 hours.

[0095] Other Aryl Aldehydes

[0096] Suitable commercially available (N,N-disubstituted)arylaminealdehydes are available form Aldrich (Milwaukee, Wis.) including, forexample, diphenylamino-benzaldehyde ((C₆H₅)₂NC₆H₄CHO) and9-ethyl-3-carbazolecarboxyaldehyde. Also, the synthesis ofN-ethyl-3,6-diformylcarbazole is decribed below in the examples.

[0097] Synthesis of Hydrazones

[0098] A hydrazine can be reacted with an appropriate aromaticaldehyde/ketone to form a desired hydrazone charge transfer compound.The reactions can be catalyzed by an appropriate amount of concentratedacid, in particular sulfuric acid. After mixing in the catalytic amountof acid with the hydrazine and aromatic aldehyde, the mixture can berefluxed for about 2 hours to about 16 hours. The initial product can bepurified by recrystalization. The synthesis of selected compounds fromthe formulas above are described below in the Examples, and the othercompounds described herein can be similarly synthesized.

[0099] In some embodiments, the hydrazines may be obtained in anacidified hydrochloride form, as noted above. For these embodiments, thehydrazine hydrochloride can be reacted with an aqueous carbonate basewhile stirring the mixture. An excess of carbonate base can be added,such as 1.2 moles of potassium carbonate for embodiments with one moleof hydrazine hydrochloride per mole hydrazine or 2.4 moles of potassiumcarbonate for embodiments with one mole of hydrazine dihydrochloride permole hydrazine. Some specific examples are presented below.

[0100] Synthesis of Second Precursor of Formula (8)

[0101] The synthesis of the second precursor can be performed byreacting a hydrazine with an aminoaryl aldehyde. The synthesis ofsuitable hydrazines is described above. Suitable aminoaryl aldehydeshave a hydroxyl group, a thiol group or a second amino group to reactwith the first precursor. Some suitable aminoaryl aldehydes arecommercially available. For example, 4-salicylaldehyde and9-formyl-8-hydroxyjulolidine are available from Aldrich. Theaminoarylaldehydes can be reacted with the hydrazines, for example, asdescribed for one embodiment in Example 1 below.

[0102] The invention will now be described further by way of thefollowing examples.

EXAMPLES Example 1 Synthesis of Charge Transfer Compound Precursors

[0103] This example described the synthesis of several intermediatesused in the sysnthesis of several specific embodiments of the chargetransfer compounds. The sythesis of the charge transfer compounds isdescribed in the next Example.

[0104] Preparation of 4-(diethylamino)salicylaldehydeN,N-diphenylhydrazone.

[0105] This example described the formation of a reactant used in theformation of several charge transport compounds in the next example.

[0106] A solution of N,N-diphenylhydrazine hydrochloride (79.5 g, 0.36mol, commercially available from Aldrich, Milwaukee, Wis.) in ethanol(500 ml) was slowly added to a solution of4-(diethylamino)salicylaldehyde (58.0 g, 0.3 mol, commercially availablefrom Aldrich, Milwaukee, Wis.) in ethanol (500 ml) to form a reactionmixture. The reaction mixture was refluxed until all aldehyde reacted,which took about 0.5 h. Then, the solvent was evaporated. After theevaporation of the solvent (800 ml), the residue was treated with ether(ethyl ether). The ether extract was washed with water until the pH ofthe wash water was neutral. The separated organic liquid was dried overanhydrous magnesium sulphate, treated with activated charcoal andfiltered. The solvent was then removed, and ethanol was added to theresidue to crystallize the product. 4-(Diethylamino)salicylaldehydeN,N-diphenyl-hydrazone (85 g; 78.8%) was filtered off and washed withethanol. The obtained hydrazone was recrystallized from the mixture of2-propanol and ether (10:1). The product was found to have a meltingpoint of 95.5-96.5° C. following recrystalization. A proton NMR spectrumwas obtained for the product. The ¹HNMR spectrum (100 MHz, CDCl₃) hadthe following peaks, ppm: 11.55 (s, 1H); 7.55-6.95 (m, 11H); 6.7 (d,J=8.6 Hz; 1H); 6.23 (s, 1H); 6.1 (d, J=8.6 Hz, 1H); 3.3 (q, J=8.0 Hz,4H); 1.1 (t, J=8.0 Hz, 6H); where s is singlet, d is doublet, m ismultiplet, q is quartet, t is triplet. An elemental analysis yielded, %:C 76.68; H 7.75; N 11.45. C₂₃H₂₅N₃O has a calculated elementaldistribution of, %: C 76.85; H 7.01; N 11.69.

[0107] Preparation of4-(Diphenylamino)benzaldehyde-N-2,3-epoxypropyl-N-Phenylhdrazone

[0108] Phenylhydrazine (0.1 mole, commercially available from Aldrich,Milwaukee, Wis.) and 4-(Diphenylamino) benzaldehyde (0.1 mole, availablefrom Fluka, Buchs SG, Switzerland) were dissolved in 100 ml ofisopropanol in a 250 ml 3-neck round bottom flask equipped with refluxcondenser and mechanical stirrer. The solution was refluxed for 2 hours.Thin layer chromatography indicated the disappearance of the startingmaterials. At the end of the reaction, the mixture was cooled to roomtemperature. The 4-(diphenylamino) benzaldehyde phenylhydrazone crystalsthat formed upon standing were filtered off and washed with isopropanoland dried in vacuum oven at 50° C. for 6 hours.

[0109] A mixture of 4-(diphenylamino) benzaldehyde phenylhydrazone (3.6g, 0.01 mole), 85% powdered potassium hydroxide (2.0 g, 0.03 mole) andanhydrous potassium carbonate in 25 ml of epichlorohydrin was stirredvigorously at 55-60° C. for 1.5-2 hours. The course of the reaction wasmonitored using thin layer chromatography on silica gel 60 F254 plates(commercially available from Merck, Whitehouse Station, N.J.) using 1:4v/v mixture of acetone and hexane as eluant. After termination of thereaction, the mixture was cooled to room temperature, diluted withether, and washed with water until the wash water had a neutral pH. Theorganic layer was dried over anhydrous magnesium sulfate, treated withactivated charcoal and filtered. Ether was removed and the residue wasdissolved in a 1:1 volume per volume mixture of toluene and isopropanol.The crystals formed upon standing were filtered off and washed withisopropanol to give 3.0 g of product (71.4% yield) with a melting pointof 141-142.5° C. The product was recrystalyzed from a 1:1 mixture oftoluene and isopropanol. The product was characterized with ¹H-NMR inCDCL3 (250 MHz instrument) with peaks observed at the following deltavalues in ppm:-7.65-6.98 (m, 19H), 6.93 (t, J=7.2 Hz, 1H), 4.35 (dd,1H), 3.99 (dd, 1H), 3.26 (m, 1H), 2.84 (dd, 1H), 2.62 (dd, 1H). Anelemental analysis yielded the following results in weight percent: %C=80.02, % H=6.31, % N=9.91, which compares with calculated values forC₂₈H₂₅N₃O of % C=80.16, % H=6.01, % N=10.02.

[0110] Preparation of9-ethyl-3-carbazolecarboxaldehyde-N-2,3-epoxypropyl-N-phenyl Hydrazone

[0111] Phenylhydrazine (0.1 mole, commercially available from Aldrich,Milwaukee, Wis.) and 9-ethyl-3-carbazolecarboxaldehyde (0.1 mole,available from Aldrich Chemical, Milwaukee, Wis.) were dissolved in 100ml of isopropanol in 250 ml 3-neck round bottom flask equipped with areflux condenser and a mechanical stirrer. The solution was refluxed for2 hours. Thin layer chromatography indicated the disappearance of thestarting materials. At the end of the reaction, the mixture was cooledto room temperature. The 9-ethyl-3-carbazolecarbaldehyde phenylhydrazonecrystals formed upon standing were filtered off and washed withisopropanol and dried in vacuum oven at 50° C. for 6 hours.

[0112] A mixture of 9-ethyl-3-carbazolecarbaldehyde phenylhydrazone (3.1g, 0.01 mole), 85% powdered potassium hydroxide (2.0 g, 0.03 mole) andanhydrous potassium carbonate in 25 ml of epichlorohydrin was stirredvigorously at 55-60° C. for 1.5-2 hours. The course of the reaction wasmonitored using thin layer chromatography on silica gel 60 F254 plates(commercially available from Merck) using 1:4 v/v mixture of acetone andhexane as eluant. After termination of the reaction, the mixture wascooled to room temperature, diluted with ether and washed with wateruntil the wash water had a neutral pH. The organic layer was dried overanhydrous magnesium sulfate, treated with activated charcoal andfiltered. Ether was removed and the residue was dissolved in a 1:1mixture of toluene and isopropanol. The crystals formed upon standingwere filtered off and washed with isopropanol to give 3.0 g of product(81.2% yield) with a melting point of 136-137° C. The product wasrecrystalyzed from 1:1 mixture of toluene and isopropanol. The productwas characterized with ¹H-NMR in CDCl₃ (250 MHz) which yielded peaks atthe following delta values in ppm: 8.35 (s, 1H), 8.14(d, J=7.8 Hz, 1H),7.93 (d, J=7.6 Hz, 1H), 7.90 (s, 1H), 7.54-7.20 (m, 8H), 6.96 (t, J=7.2Hz, 1H), 4.37 (m, 3H), 4.04 (dd, J1=4.3 Hz, J2=16.4 Hz, 1H), 3.32 (m,1H), 2.88 (dd, 1H), 2.69 (dd, 1H), 1.44 (t, J=7.2 Hz, 3H). Elementalanalysis yielded the following results in weight percent % C=78.32, %H=6.41, % N=11.55; which compares with calculated values for C₂₄H₂₃N₃Oof % C=78.02, % H=6.28, N %=11.37.

[0113] Preparation of4-dimethylaminobenzaldehyde-N-2,3-epoxypropyl-N-phenylhydrazone

[0114] The preparation of4-dimethylaminobenzaldehyde-N-2,3-epoxypropyl-N-phenylhydrazone wasperformed as described above for4-(diphenylamino)benzaldehyde-N-2,3-epoxypropyl-N-phenylhydrazone exceptthat 4-(dimethylamino)benzaldehyde (Aldrich) was used instead of4-(Diphenylamino) benzaldehyde.

[0115] Preparation of4-(4,4′-di(methylphenyl)amino)benzaldehyde-N-2,3-epoxypropyl-N-phenylhydrazone

[0116] The preparation of4-(4,4′-di(methylphenyl)amino)benzaldehyde-N-2,3-epoxypropyl-N-phenylhydrazonewas performed as described above for4-(diphenylamino)benzaldehyde-N-2,3-epoxypropyl-N-phenylhydrazone exceptthat 4-(4,4′-di(methylphenyl)amino)benzaldehyde (Aldrich) was usedinstead of 4-(Diphenylamino)benzaldehyde.

[0117] Preparation of4-diethylaminobenzaldehyde-N-2,3-epoxypropyl-N-Phenylhydrazone

[0118] The preparation of4-diethylaminobenzaldehyde-N-2,3-epoxypropyl-N-phenylhydrazone wasperformed as described above for4-(diphenylamino)benzaldehyde-N-2,3-epoxypropyl-N-phenylhydrazone exceptthat 4-(diethylamino)benzaldehyde (Aldrich) was used instead of4-(Diphenylamino) benzaldehyde.

Example 2 Synthesis of Charge Transport Compounds

[0119] This example describes the synthesis of five charge transportcompounds corresponding to formulas 2-6 above.

[0120] Compound 2

[0121] A 0.6 ml (4.45 mmol) quantity of triethylamine (TEA) was added toa mixture of 4-(diethylamino)salicylaldehyde N,N-diphenylhydrazone (4.0g, 11.13 mmol) and 4-(diphenylamino)benzaldehydeN-2,3-epoxypropyl-N-phenylhydrazone (4.67 g, 11.13 mmol) and 15 ml of2-butanone. The mixture was refluxed until one of the starting compoundsdisappeared, which required 38 hours, as determined by thin layerchromatography (TLC) using silica gel 60 F254 plates, commerciallyavailable from Merck, and 1:4 v/v mixture of acetone and hexane aseluent. At the end of the reaction, 2-butanone and TEA were distilledoff and the residue was subjected to chromatography using a columnpacked with silica gel (Merck grade 9385, commercially obtained fromAldrich, Milwaukee, Wis.) and a 4:1 v/v solution of hexane and acetoneas the eluant. The product was crystallized from a mixture of 2-propanoland ether (10:1). The crystals formed were filtered off and washed withthe mixture of 2-propanol and n-hexane (1:1) to give 6.5 g (74.7%) ofCompound 2. The product had a melting point of 161-162° C. aftercrystalization from 10:1 v/v of 2-propanol and ether. A ¹HNMR spectrum(250 MHz, CDCl₃) yielded the following peaks, ppm: 7.85 (d, J=8.8 Hz;1H); 7.60-6.92 (m, 31H); 6.37 (d, J=8.8 Hz; 1H); 6.02 (s, 1H); 4.18 (m,1H); 4.03-3.68 (m, 4H); 3.31 (q, J=7.1 Hz; 4H); 2.64 (d, J=6.5 Hz; 1H);1.11 (t, J=7.1 Hz; 6H). An elemental analysis yielded, %: C 78.44; H6.29; N 10.61. C₅₁H₅₀N₆O₂ has a calculated elemental distribution of %:C 78.64; H 6.47; N 10.79.

[0122] Compound 3

[0123] Compound 3 was prepared and isolated following the procedure usedto prepare Compound 2 except that instead of4-(diphenylamino)benzaldehyde N-2,3-epoxypropyl-N-phenylhydrazone,9-ethyl-3-carbazolecarboxaldehyde N-2,3-epoxypropyl-N-phe-nylhydrazone(4.11 g, 11.13 mmol) was used. The yield was 5.9 g (72.8%) and theproduct had a melting point of 108.5-109.5° C. after crystalization from10:1 v/v of 2-propanol and ether. A ¹HNMR spectrum (250 MHz, CDCl₃) hadpeaks at, ppm: 8.17 (s, 1H); 8.12 (d, J=7.5 Hz; 1H); 7.94 (d, J=8.8 Hz;1H); 7.85 (d, J=7.6 Hz; 1H); 7.74 (s, 1H); 7.61 (s, 1H); 7.55-6.96 (m,19H); 6.38 (d, J=8.8 Hz; 1H); 6.02 (s, 1H); 4.37 (q, J=7.3 Hz; 2H); 4.25(m, 1H); 4.03-3.72 (m, 4H); 3.26 (q, J=7.1 Hz; 4H); 2.72 (d, J=7.2 Hz;1H); 1.44 (t, J=7.1 Hz; 3H); 1.06 (t, J=7.1 Hz; 6H). An elementalanalysis yielded, %: C 77.21; H 6.48; N 11.68. C₄₇H₄₈N₆O₂ has acalculated elemental distribution of, %: C 77.44; H 6.64; N 11.53.

[0124] Compound 4

[0125] Compound 4 was prepared following the procedure used to prepareCompound 2 except that instead of 4-(diphenylamino)benzaldehydeN-2,3-epoxypropyl-N-phenylhydrazone, 4-dimethylaminobenzaldehydeN-2,3-epoxypropyl-N-phenyl-hydrazone (3.29 g, 11.13 mmol) was used. Thereaction time was 34 h. After removal of the solvent, the residue wascrystallized from a mixture of toluene and 2-propanol. The yield was 4.8g (65.8%), and the product had a melting point of 159.5-160.5° C. whencrystallized from the mixture of toluene and 2-propanol. A ¹HNMRspectrum (250 MHz, CDCl₃) yielded peaks at, ppm: 7.88 (d, J=8.8 Hz; 1H);7.55 (s, 1H); 7.48 (m, 3H); 7.36-6.92 (m, 17H); 6.69 (d, J=8.9 Hz; 2H);6.38 (d, J=8.8 Hz; 1H); 6.02 (s, 1H); 4.17 (m, 1H); 3.99-3.62 (m, 4H);3.31 (q, J=7.1 Hz; 4H); 2.98 (s, 6H); 2.79 (d, J=6.5 Hz; 1H); 1.12 (t,J=7.1 Hz; 6H). An elemental analysis yielded, %: C 75.01; H 6.91; N12.68. C₄₁H₄₆N₆O₂ has a calculated elemental distribution of, %: C75.20; H 7.08; N 12.83.

[0126] Compound 5

[0127] Compound 5 was prepared and isolated following the procedure usedto prepare Compound 2 except that instead of4-(diphenylamino)benzaldehyde N-2,3-epoxypro-pyl-N-phenylhydrazone,4-(4,4′-dimethyldiphenylamino)benzaldehydeN-2,3-epoxypropyl-N-phenylhydrazone (4.98 g, 11.13 mmol) was used.Compound 5 was obtained as an oil at a yield of 6.8 g (76.4%). A ¹HNMRspectrum (100 MHz, CDCl₃) yielded peaks at, ppm: 7.9 (d, J=8.8 Hz; 1H);7.7-6.9 (m, 29H); 6.4 (d, J=8.8 Hz; 1H); 6.05 (s, 1H); 4.3 (m, 1H);4.1-3.7 (m, 4H); 3.35 (q, J=7.1 Hz; 4H); 2.65 (m, 1H); 2.4 (s, 6H); 1.15(t, J=7.1 Hz; 6H). AN elemental analysis yielded, %: C 78.69; H 6.58; N10.60. C₅₃H₅₄N₆O₂ has a calculated elemental distribution of, %: C78.88; H 6.74; N 10.41.

[0128] Compound 6

[0129] Compound 6 was prepared and isolated following the procedure usedto prepare Compound 2 except that instead of4-(diphenylamino)benzaldehyde N-2,3-epoxypropyl-N-phenylhydrazone,4-diethylaminobenzaldehyde N-2,3-epoxypropyl-N-phenyl hydrazone (3.60 g,11.13 mmol) was used. The yield was 5.2 g (67.5%), and the product had amelting point of 140.5-142° C. when crystallized from 10:1 v/v of2-propanol and ether). A ¹HNMR spectrum (250 MHz, CDCl₃) yielded peaksat, ppm: 7.87 (d, J=8.8 Hz; 1H); 7.55 (s, 1H); 7.49 (s, 1H); 7.45 (d,J=5.7 Hz; 2H); 7.40-6.89 (m, 15H); 6.63 (d, J=8.9 Hz; 2H); 6.38 (d,J=8.8 Hz; 1H); 6.02 (s, 1H); 4.17 (m, 1H); 3.99-3.62 (m, 4H); 3.45 (m,8H); 2.83 (d, J=6.5 Hz; 1H); 1.12 (m, 12H). An elemental analysisyielded, %: C 75.45; H 7.11; N 12.51. C₄₃H₅₀N₆O₂ has a calculatedelemental distribution of, %: C 75.63; H 7.38; N 12.31.

Example 3 Charge Mobility Measurements

[0130] This example describes the measurement of charge mobility forsamples formed with the five charge transport compounds described inExample 2. Some samples included a polymer binder while other samplesdid not.

[0131] Sample 1

[0132] A mixture of 0.1 g of Compound 2 and 0.1 g of polyvinylbutyral(Aldrich 41,843-9) was dissolved in 2 ml of THF. The solution was coatedon a polyester film with conductive aluminum layer by the dip rollermethod. After drying for 15 min. at 80° C. temperature, a clear 10 μmthick layer was formed.

[0133] Sample 2

[0134] A 0.24 g quantity of Compound 3 was dissolved in 1 ml of THF. Thesolution was coated on the polyester film with conductive aluminum layerby the dip roller method. After drying for 15 min. at 80° C.temperature, a clear 5 μm thick layer of good quality of Compound 3 wasformed.

[0135] Sample 3

[0136] The sample was prepared according to the procedure for Sample 1,except that Compound 3 was used in place of Compound 2.

[0137] Sample 4

[0138] A thin layer of Compound 4 was prepared according to theprocedure for Sample 2 with Compound 4 replacing Compound 3.

[0139] Sample 5

[0140] The sample was prepared according to the procedure for Sample 1,except that Compound 4 was used in place of Compound 2.

[0141] Sample 6

[0142] The sample was prepared according to the procedure for Sample 1,except Compound 5 was used in place of Compound 2.

[0143] Sample 7

[0144] The sample was prepared according to the procedure for Sample 1,except Compound 6 was used in place of Compound 2.

[0145] Mobility Measurements

[0146] Each sample was corona charged positively up to a surfacepotential U, illuminated with 2 ns long nitrogen laser light pulse andthe hole mobility μ was determined as described in Kalade et al.,“Investigation of charge carrier transfer in electrophotographic layersof chalkogenide glases,” Proceeding IPCS 1994: The Physics and Chemistryof Imaging Systems, Rochester, N.Y., pp. 747-752, incorporated herein byreference. This hole mobility measurement was repeated changing thecharging regime and charging the sample to different U values, whichcorresponded to different electric field strength inside the layer E.This dependence was approximated by the formula

μ=μ₀ e ^(α{square root}{square root over (E)}).

[0147] Here E is electric field strength, μ₀ is the zero field mobilityand α is Pool-Frenkel parameter. The mobility characterizing parametersμ₀ and α values as well as the mobility value at the 6.4×10⁵ V/cm fieldstrength as determined from these measurements are given in Table 1.TABLE 1 μ₀ μ(cm²/V · s) at Sample (cm²/V · s) 6,4 · 10⁵ V/cm α(cm/V)^(1/2) 1 2.1 · 10⁻⁹ 7.7 · 10⁻⁸ 0.0045 2 7.0 · 10⁻⁸ 6.7 · 10⁻⁶0.0057 3 1.1 · 10⁻⁹ 1.5 · 10⁻⁷ 0.0061 4 5.7 · 10⁻⁷ 2.9 · 10⁻⁵ 0.0049 51.7 · 10⁻⁸ 1.5 · 10⁻⁶ 0.0056 6 7.1 · 10⁻⁹ 3.9 · 10⁻⁷ 0.0050 7 1.6 · 10⁻⁸1.3 · 10⁻⁶ 0.0055

Example 4 Ionization Potential Measurements

[0148] This example describes the measurement of the ionizationpotential for the five charge transport compounds described in Example2.

[0149] To perform the ionization potential measurements, a thin layer ofcharge transport compound about 0.5 μm thickness was coated from asolution of 2 mg of charge transport compound in 0.2 ml oftetrahydrofuran on a 20 cm substrate surface. The substrate waspolyester film with an aluminum layer over a methylcellulose sublayer ofabout 0.4 μm thickness.

[0150] Ionization potential was measured as described in Grigaleviciuset al., “3,6-Di(N-diphenylamino)-9-phenylcarbazole and itsmethyl-substituted derivative as novel hole-transporting amorphousmolecular materials,” Synthetic Metals 128 (2002), p. 127-131,incorporated herein by reference. In particular, each sample wasilluminated with monochromatic light from the quartz monochromator witha deuterium lamp source. The power of the incident light beam was2-5-10⁻⁸ W. The negative voltage of −300 V was supplied to the samplesubstrate. The counter-electrode with the 4.5×15 mm² slit forillumination was placed at 8 mm distance from the sample surface. Thecounter-electrode was connected to the input of the BK2-16 typeelectrometer, working in the open impute regime, for the photocurrentmeasurement. A 10⁻¹⁵-10⁻¹² amp photocurrent was flowing in the circuitunder illumination. The photocurrent, I, was strongly dependent on theincident light photon energy hv. The I^(0.5)=f(hv) dependence wasplotted. Usually the dependence of the square root of photocurrent onincident light quanta energy is well described by linear relationshipnear the threshold [see references “Ionization Potential of OrganicPigment Film by Atmospheric Photoelectron Emission Analysis,”Electrophotography, 28, Nr. 4, p. 364 (1989) by E. Miyamoto, Y.Yamaguchi, and M. Yokoyama; and “Photoemission in Solids,” Topics inApplied Physics, 26, 1-103 (1978) by M. Cordona and L. Ley, both ofwhich are incorporated herein by reference]. The linear part of thisdependence was extrapolated to the hν axis and Ip value was determinedas the photon energy at the interception point. The ionization potentialmeasurement has an error of ±0.03 eV. The ionization potential valuesare given in Table 2. TABLE 2 Ionization Potential Compound I_(P) (eV) 25.27 3 5.22 4 5.20 5 5.28 6 5.19

[0151] As understood by those skilled in the art, additionalsubstitution, variation among substituents, and alternative methods ofsynthesis and use may be practiced within the scope and intent of thepresent disclosure of the invention. The embodiments above are intendedto be illustrative and not limiting. Additional embodiments are withinthe claims. Although the present invention has been described withreference to particular embodiments, workers skilled in the art willrecognize that changes may be made in form and detail without departingfrom the spirit and scope of the invention.

What is claimed is:
 1. An organophotoreceptor comprising at least onephotoconductive element comprising: (a) a charge transport compoundhaving the formula

where R₁ is a carbazole group, a julolidine group, or ap-(N,N-disubstituted)arylamine, R₂, R₃, R₄, R₅ and R₆ are,independently, an alkyl group or an aryl group, R₇ and R₈ are,independently, hydrogen, an alkyl group, or an aryl group, X is oxygen,sulfur, or a NR′ group where R′ is hydrogen, an alkyl, or an aryl group,and Y is an aryl group; and (b) a charge generating compound; whereinthe at least one photoconductive element is on an electricallyconductive substrate.
 2. An organophotoreceptor according to claim 1wherein the at least one photoconductive element further comprises anelectron transport compound.
 3. An organophotoreceptor according toclaim 1 wherein the charge transport compound has the formula

where R₁ is a carbazole group, a julolidine group, or ap-(N,N-disubstituted)arylamine, and R₃ and R₄ are, independently, analkyl group or an aryl group.
 4. An organophotoreceptor according toclaim 1 wherein the at least one photoconductive element furthercomprises a binder.
 5. An organophotoreceptor according to claim 1wherein the charge transport compound has a formula selected from thegroup consisting of the following:


6. An electrophotographic imaging apparatus comprising: (a) a lightimaging component; and (b) an organophotoreceptor oriented to receivelight from the light imaging component, the organophotoreceptorcomprising an electrically conductive substrate and a photoconductiveelement on the electrically conductive substrate, the photoconductiveelement comprising (i) a charge transport compound having the formula

where R₁ is a carbazole group, a julolidine group, or ap-(N,N-disubstituted)arylamine, R₂, R₃, R₄, R₅ and R₆ are,independently, an alkyl group or an aryl group, R₇ and R₈ are,independently, hydrogen, an alkyl group, or an aryl group, X is oxygen,sulfur, or a NR′ group where R′ is hydrogen, an alkyl, or an aryl group,and Y is a aryl group; and (ii) a charge generating compound.
 7. Anelectrophotographic imaging apparatus according to claim 6 wherein thecharge transport compound has the formula

where R₁ is a carbazole group, a julolidine group, or ap-(N,N-disubstituted)arylamine, and R₃ and R₄ are, independently, analkyl group or an aryl group.
 8. An electrophotographic imagingapparatus according to claim 6 wherein the charge transport compound hasa formula selected from the group consisting of the following:


9. An electrophotographic imaging apparatus according to claim 6 whereinthe at least a photoconductive element further comprises an electrontransport compound.
 10. An electrophotographic imaging apparatusaccording to claim 6 wherein the at least a photoconductive elementfurther comprises a binder.
 11. An electrophotographic imaging apparatusaccording to claim 6 further comprising a liquid toner dispenser.
 12. Anelectrophotographic imaging process comprising: (a) applying anelectrical charge to a surface of an organophotoreceptor comprising anelectrically conductive substrate and a photoconductive element on theelectrically conductive substrate, the photoconductive elementcomprising (i) a charge transport compound having the formula

where R₁ is a carbazole group, a julolidine group, or ap-(N,N-disubstituted)arylamine, R₂, R₃, R₄, R₅ and R₆ are,independently, an alkyl group or an aryl group, R₇ and R₈ are,independently, hydrogen, an alkyl group, or an aryl group, X is oxygen,sulfur, or a NR′ group where R′ is hydrogen, an alkyl, or an aryl group,and Y is a aryl group; and (ii) a charge generating compound; (b)imagewise exposing the surface of the organophotoreceptor to radiationto dissipate charge in selected areas and thereby form a pattern ofcharged and uncharged areas on the surface; (c) contacting the surfacewith a toner to create a toned image; and (d) transferring the tonedimage to a substrate.
 13. An electrophotographic imaging processaccording to claim 12 wherein the charge transport compound has theformula

where R₁ is a carbazole group, a julolidine group, or ap-(N,N-disubstituted)arylamine, and R₃ and R₄ are, independently, analkyl group or an aryl group.
 14. An electrophotographic imaging processaccording to claim 12 wherein the charge transport compound has aformula selected from the group consisting of the following:


15. An electrophotographic imaging process according to claim 12 whereinthe photoconductive element further comprises an electron transportcompound.
 16. An electrophotographic imaging process according to claim12 wherein the photoconductive element further comprises a binder. 17.An electrophotographic imaging process according to claim 12 wherein thetoner comprises a liquid toner comprising a dispersion of colorantparticles in an organic liquid.
 18. A charge transport compound havingthe formula

where R₁ is a carbazole group, a julolidine group, or ap-(N,N-disubstituted)arylamine, R₂, R₃, R₄, R₅ and R₆ are,independently, an alkyl group or an aryl group, R₇ and R₈ are,independently, hydrogen, an alkyl group, or an aryl group, X is oxygen,sulfur, or a NR′ group where R′ is hydrogen, an alkyl, or an aryl group,and Y is a aryl group.
 19. A charge transport compound according toclaim 18 having the formula

where R₁ is a carbazole group, a julolidine group, or ap-(N,N-disubstituted)arylamine, and R₃ and R₄ are, independently, analkyl group or an aryl group.
 20. A charge transport compound accordingto claim 18 wherein the charge transport compound has a formula selectedfrom the group consisting of the following: